The present invention relates generally to multiple clutches or multiple disc clutches and, more particularly though not exclusively, to clutches comprising two clutch discs for use in motor vehicles, generally known as double disc clutches which have only one output or clutches known as dual clutches which have two outputs.
As is known such clutches comprise a reaction plate or flywheel which is generally fixed for rotation with a driving shaft and a plurality of parts forming a unitary assembly generally known as the cover assembly which is mounted on the reaction plate and a clutch disc or plate disposed between the reaction plate and the cover assembly and fixed for rotation with the driven shaft.
As is known, when a clutch comprises two clutch discs it comprises an annular member called a cover forming a housing and adapted to be mounted on the reaction plate, and two axially spaced annular plates called pressure plates which clamp or press therebetween the intermediate clutch disc, and resilient means bearing against the cover and constantly biasing the pressure plates away from the cover and disengagement means provided for each of the pressure plates for returning them toward the cover.
For multiple clutches two or more pressure plates are provided alternating with the clutch discs, in double disc clutches the inner clutch disc between the two pressure plates is fixed for rotation with the same driven shaft as the outer clutch disc which is between the terminal pressure plate and the reaction plate. In the case of a dual clutch the inner clutch disc is fixed for rotation with another driven shaft. In any event in the clutch engaged position the clutch discs are both clamped or pressed. When the clutch is disengaged the clutch discs are released or unclamped and in order to avoid any residual friction which is inevitably a source of wear of the facings of the clutch discs, the pressure plates associated therewith are subjected to disengagement or separating means which exert a return action thereon.
The disengagement or separating means associated with the outer clutch disc between the outer pressure plate and the reaction plate normally safely ensures the release of the clutch disc since the terminal pressure plate which is then urged toward the cover necessarily moves away from the reaction plate. But this is not necessarily so for the inner clutch disc between the two pressure plates. Under the action of their disengagement means the pressure plates are both returned or urged toward the cover. Unless other measures are taken they may clamp around the inner clutch disc therebetween.